In previous publications (1,2) from this station, we have shown that a person on recovering from an infection produced by Plasmodium vivax acquires an immunity to this parasite. This immunity possesses a very effective homologous specificity and very definite, though less effective, heterologous qualities (3). It is therefore of interest to ascertain whether recovery from infections with Plasmodium falciparum results in the acquirement of an analogous immunity.
The subjects of these experiments were all negroes, patients for whom malaria therapy had been prescribed. It is necessary to employ P. falciparum for this purpose in order to secure an attack of sufficient intensity to be of therapeutic effect, as we have shown (4) that negroes commonly possess an appreciable natural tolerance to P. vivax.
I. HOMOLOGOUS IMMUNITY The strain of P. falciparum employed, which we designate as “Coker” was captured in lot 87 of A. quadrimaculatus in 1932 from an autochthonous case occurring in a young negro patient in the hospital.